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Prehistoric Earth

Dinosaurs' feet and legs were tremendously varied. Most of the large, four-legged plant-eaters had sturdy limbs and broad feet like an elephant's. Two-legged dinosaurs had long, birdlike feet and three toes, tipped with sharp claws or hooflike nails. Four-legged dinosaurs usually plodded along, but some two-legged dinosaurs were as fast as a horse. Scientists can tell how quickly a dinosaur moved by comparing it with mammals or birds of today with similar bone structure, or by studying dinosaur...

The sauropods were the tallest, longest, and heaviest animals ever to walk the Earth. Fully grown, some weighed as much as 15 African elephants. Size was their main form of self-defense - they were simply too big to attack. And this was not the only advantage of being a giant. Standing high off the ground, a sauropod could crop leafy twigs out of reach of all other plant-eating dinosaurs. Sauropods were strictly herbivorous. Like leaf-eaters today, they would have had to spend nearly all their...

Not all dinosaurs were docile plant-eaters. The flesh-eating dinosaurs -theropods - had to kill to survive. Lethal weapons equipped these animals for a life of violence razor-sharp fangs, claws like grappling hooks, powerful jaws for tearing flesh, and muscular legs to stamp the life out of small victims. Many would have preyed on small fry - baby dinosaurs, lizards, or eggs. Others may have ganged together, using stealth and cunning to trap larger victims, and teamwork to overwhelm them. One...

Above the dinosaurs flapped and soared strange, bat-like reptiles -the pterosaurs. Some were as small as sparrows, but others had the wingspan of a light aircraft. All had slim, hollow bones and wings made of skin that stretched between enormously long finger-bones and the legs. Like bats and birds today, pterosaurs may have been warmblooded and furry. Most were fish-eaters that lived much like those seabirds the terns and frigate birds. There may also have been pterosaur swallows that caught...

Dinosaurs were among the most amazing and successful animals ever. From ancestors no bigger than dogs, they evolved into gigantic killers as heavy as elephants, plant-eaters several bus-lengths long, and nimble little creatures the size of chickens. While they ruled the land, no mammal larger than a domestic cat survived. Dinosaurs first appeared about 230 million years ago and flourished for an astonishing 165 million years. Then, 65 million years ago, they suddenly and mysteriously...

Imagine a monster with teeth the size of daggers peering at you through an upstairs window. Lunging in, it snatches you in its immense jaws and swallows you whole. In the Age of Dinosaurs such creatures were no nightmare but terrible reality. The flesh-eating dinosaurs - theropods - evolved into giants because they had to tackle enormous prey. But as a result JP their prey became ever larger for w f protection. It is as if the flesh-eaters and plant-eaters became locked in an evolutionary arms...

People once thought that many dinosaurs were too heavy to live out of water and had to wallow in lakes, their long necks serving as snorkels. But careful studies have shown that all dinosaurs lived and walked on land. The biggest were four-legged with heavy club feet, so they probably moved slowly like elephants. Smaller two-legged dinosaurs were swifter and more nimble. The long-legged ornithomimids (ostrich mimics) were probably the quickest, capable of sprinting at sustained high speeds....

Dinosaurs tended to have shorter arms than legs because they evolved from two-legged running ancestors that used their arms just for grabbing prey. Most predatory dinosaurs kept this build, their short arms ending in three clawed fingers, though some had two or five. In the four-legged plant-eaters, arms evolved into stout props to support the body, yet they were usually shorter than the hindlegs. Most plant-eaters had four or five padded, blunt-nailed fingers that served as hooves but in some...

Like yours, a dinosaur's skull protected its brain and housed organs for sight, smell, and hearing as well as its airways, jaws, and teeth. Most dinosaur skulls had windows to save weight or take jaw muscles, but there was a great range of sizes and shapes. Sauropods, the largest dinosaurs, had heads no bigger than those of horses, yet the much smaller horned dinosaurs had skulls up to 10 ft 3 m long - the largest heads of any land animal. But even the biggest dinosaur skulls housed brains with...

Every year, many animals set off on long-distance journeys to find food or breeding sites. Their journeys are called migrations. In North America, caribou trek thousands of miles north every spring to feed in the Arctic. In autumn, they head south again to escape the bitter northern winter. Birds cover even greater distances - in a single year the Arctic tern can fly up to 12,000 miles 20,000 km . Dinosaurs may have migrated for much the same reason. Our strongest clues that they did so are...

Fossilized dinosaur eggs have been found all over the world, sometimes in vast numbers. One Spanish site holds 300,000. These were probably laid at a mass-breeding ground that dinosaurs returned to each year. There are about 40 different kinds of dinosaur egg, from cannonballs and long loaves to tiny eggs that would fit in your hand. Like birds' eggs, they all had hard shells. A few contain babies' bones, clues to the kind of dinosaur that laid them. Fossilized mud nests with the remains of...

If you went scuba diving during the Cretaceous Period, the underwater world would have looked much as it does today. The seas teemed with familiar animals - jellyfish, corals, oysters, crabs, snails, and a bewildering variety of fish, including sharks. But you might also have caught sight of some of the weird and wonderful reptiles that once lived in the oceans. Like dolphins and whales, the marine reptiles evolved from land animals that returned to the sea. These monsters of the deep dominated...

About 75 million years ago there were more kinds of dinosaur than ever yet 10 million years later all but the birds had vanished. Indeed, no land animal heavier than a large dog survived. Also gone were the pterosaurs and many sea creatures. At least 80 theories have tried to explain how so much life was wiped off the face of the Earth. Most are absurd - no one still thinks that dinosaurs became too large to breed, for instance. But experts argue to this day about what must have happened....

The word dinosaur makes us think of gigantic animals, yet dinosaurs came in a surprisingly wide range of sizes. The average dinosaur was probably no heavier than a horse, and many were far smaller. It may even be that fewer kinds of dinosaur weighed over a ton than did prehistoric land mammals before human hunters began killing big mammals off . But as the fossil record proves, many dinosaurs were colossal. The biggest of them all - the long-necked sauropods - were the heaviest, longest, and...

Nobody knows how any dinosaur was colored. Pigments, the coloring ingredients in skin, rarely survive with fossil bones. But at least we can make sensible guesses. Our best clues come from living relatives of dinosaurs - birds and crocodiles - and from animals that resemble them in size or lifestyle, such as large mammals. From these it seems likely that many dinosaurs had camouflage patterns and colors to help them hide from enemies. Brightly colored skins or crests may have helped some...

Scientists once thought that all big flesh-eating dinosaurs ate only large plant-eating dinosaurs. Then fossil hunters discovered the spinosaurs -a group of large flesh-eaters with jaws and teeth made to eat sizable fish. There may have been other groups of dinosaurs with specialized diets, too. For instance, wide-mouthed dinosaurs may have been unfussy browsers, whereas narrow-mouthed plant-eaters probably chose what they ate. Using its curved thumb claws as meat hooks, Suchomimus could have...

Predators, rivals, parasites, diseases, and injuries would have killed off most before they grew old. The deadliest threats were the fangs and claws of big predators like Tyrannosaurus. Most dinosaurs were too big to burrow or climb, so they relied on other kinds of protection from these killers. Hatchlings may have stayed in thick vegetation, perhaps using camouflage to hide. Ostrich dinosaurs outran their attackers, and ankylosaurs were protected by body armor....

Dinosaurs, like humans, belong to a group of animals called vertebrates. The key feature of all vertebrates is the spine - a stiff rod made up of small bones running from the head to the tail. The spines of dinosaurs reveal a great deal about the way they moved. In some dinosaurs, the bones of the spine were joined by flexible joints, allowing these dinosaurs to swing their necks and tails at will. In others, rodlike stiffeners made parts of the spine rigid. The rear part of the spine formed...